Hello, I have an old recipe for mixing a good barrel cleaner for copper fouling. it is: 1 oz. Ammonium persulphate, 200 gr ammonmium carbonate, 6oz. stronger ammonia, 4 oz. water. I tried to get the first ingredient at a drugstore, the ammonium persulphate and they never heard of it nor could they find it listed from their suppliers. Is there a substitute for that? The next ingredient is ammonium carbonate (they have that) but what is 200 gr? grains or grams?? thanks, willp